# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

A self-hosted LinkedIn Post Formatter that converts text with formatting markers (`**bold**`, `_italic_`) into Unicode Mathematical Alphanumeric Symbols. LinkedIn only accepts plain Unicode text (no HTML/Markdown), so the tool converts text into Unicode variants that *appear* formatted in the LinkedIn feed.

## Running the Project

```bash
npm start                  # Start server on port 3000
PORT=8080 node server.js   # Custom port
docker compose up -d       # Docker deployment
```

There are no build, test, or lint steps.

## Architecture

The project is intentionally minimal:

- **`server.js`** — 16-line Express server that only serves static files from `public/` and supports a `PORT` env var.
- **`public/index.html`** — The entire application: HTML, CSS, and JavaScript all inlined in one file (~289 lines). No frameworks, no bundler, no external dependencies.

All formatting logic lives in `public/index.html` as vanilla JavaScript:

- `applyInline(text, variant)` — Processes `**text**` (bold) and `_text_` (italic) markers within a variant pass
- `mapAll(text, map)` — Applies Unicode character mapping char-by-char
- `liParagraph(text)` — Inserts zero-width spaces (`\u200b`) between double newlines to preserve paragraph breaks when pasting into LinkedIn (which strips trailing blank lines)
- Six output variants: Sans (standard), Bold Sans, Italic Sans, Bold Italic Sans, Monospace, Plain

The Unicode character maps are JavaScript objects mapping A–Z, a–z, 0–9 to their Unicode Mathematical Alphanumeric equivalents (e.g., bold sans, italic sans, monospace).

## Key Implementation Details

**Zero-width space trick:** LinkedIn strips trailing blank lines on paste. The app inserts `\u200b` between `\n\n` sequences to preserve paragraph structure.

**Character limit:** LinkedIn max is 3000 characters. The counter uses color-coded feedback (green → amber → red) with `toLocaleString('de-DE')` formatting.

**Clipboard fallback:** Uses `navigator.clipboard.writeText()` with a `document.execCommand('copy')` fallback for older browsers.

**Keyboard shortcuts:** Ctrl/Cmd+B (bold), Ctrl/Cmd+I (italic), Ctrl/Cmd+Enter (generate preview).

## Language

The UI and all user-facing text is in **German**. Keep new UI additions in German.